Win 7 Reload from USB.

I followed the tech article on how to reload Windows 7 from a USB and prepared the USB OK but wanted to confirm how to actually do the deed.
Do You boot with the USB inserted or do you need to change boot order etc?
I have OEM Ultimate on a Sony Viao which came loaded with W7 Premium, both in German. I wanted to use the trick to replace with Win7 Ultimate English.